A FORMER senior executive of British Gas - one of the world's biggest energy companies - has been convicted of two counts of insider trading in the New South Wales Supreme Court.

Stuart Alfred Fysh, a former executive vice-president at British Gas (now known as BG Group Plc) was sentenced to two terms of imprisonment, worth two years and 18 months separately, on Wednesday.

The former high-flying executive, who earned in excess of $1.3 million a year before his employment with BG came to an end, was convicted of two counts of insider trading relating to his purchase of Queensland Gas Company (QGC) shares in December 2007.

The illegal trades made him a net profit of $626,703.

Justice Lucy McCallum directed that Fysh be released on December 10, 2013, if he behaves well while in prison for 12 months.

In sentencing Fysh, Justice McCallum said he had co-operated with authorities in an ''exceptional'' way, demonstrating a ''strong willingness to facilitate the course of justice''. But Justice McCallum said she remained ''equivocal … as to whether the offender's contrition extends to a real acceptance of the proposition that he has committed two serious criminal offences''.

''In all the circumstances of this case, I am satisfied that no other sentence than imprisonment will adequately reflect the seriousness of the offences,'' she said.

For the offence of acquiring 240,000 shares in QGC on December 2, 2007, while in possession of inside information, Fysh was sentenced to two years in prison, to be released on December 10, 2013, pending good behaviour. For acquiring 10,000 shares in QGC on December 3, 2007, while in possession of inside information, he was sentenced to 18 months in prison, to be released on December 10, 2013, pending good behaviour.

The original charges - brought by the Australian Securities and Investments Commission - were in relation to Fysh's purchase of shares in two companies: Arrow Energy in mid-2007 and Queensland Gas in December 2007.

Fysh was found guilty in November of two charges relating to his purchase of Queensland Gas shares, but he was not found guilty of the two charges regarding his purchase of Arrow shares.